In order to generate sound in telephones, it is necessary to produce a signal with any waveform and an adjustable voltage level (amplitude). The signal generated in this manner can then be transformed into sound waves with the aid of capacitive sound transducers, for example.
For multi-tone calling, in particular, such as used in modern telephony, it is necessary to provide a circuit arrangement that can generate the signal described above in the desired waveform. Known circuit arrangements use a relatively high constant supply voltage for this purpose in order to derive the desired signal with the aid of an appropriate voltage transformer.